Ingredient review
PET Copolymer
INCI: PENTAERYTHRITOL/TEREPHTHALIC ACID COPOLYMER
A synthetic polymer that creates a flexible, water-resistant film on skin or lashes to help makeup last longer.
In plain English
This is a man-made plastic-like ingredient that forms a thin, flexible, invisible film on your skin or lashes. It's most often found in long-wear makeup like mascara, eyeliner, and foundation to help them stay put through sweat, humidity, and tears. Think of it as a clear, breathable raincoat for your makeup.
Review score
Safety, usefulness, and evidence
Potentially useful with some tradeoffs
The evidence base is useful, but some claims depend heavily on the formula.
Risk flags are low for most users, though the finished product can still irritate.
- Source
- synthetic
- Evidence
- moderate
- Irritation
- low
- Clogging risk
- low
Quick decision guide
Useful, but context matters
PET Copolymer is generally a lower-concern ingredient when the full formula suits your skin.
Plain-English read
Treat this as a practical screening step before you compare products that contain this ingredient.
- Step 1Start with the score, then check the irritation and clogging risk before judging PET Copolymer.
- Step 2Use the "Best for" and "Use caution if" sections to match the ingredient to your skin, not just to a marketing claim.
- Step 3If a product stings, breaks you out, or worsens irritation, judge the finished formula and stop using it even if the ingredient scores well.
Score terms in plain English
Irritation risk
lowLess likely to sting, burn, or bother most users, though sensitive skin can still react.
Clogging risk
lowLess likely to feel heavy or contribute to clogged pores for most skin types.
Evidence level
moderateThere is useful support, but formula details and claim strength still matter.
What it is
A synthetic copolymer made from pentaerythritol and terephthalic acid. It belongs to the polyester family and is engineered specifically for cosmetics to create a durable, water-resistant film.
How it works
When applied, the liquid polymer dries and links together into a continuous, flexible film. This film physically locks pigment and other ingredients in place, preventing them from smudging, flaking, or transferring. It also helps control the thickness and spreadability of the product.
Pros
Excellent wear time
Helps mascara and eyeliner stay put all day without smudging, even in humid conditions.
Water-resistant barrier
Creates a protective film that resists sweat, tears, and rain, so your makeup stays intact longer.
Cons and cautions
Can feel stiff
Some users report a tight or stiff sensation on lashes or skin, especially if the formula contains a high concentration.
Requires oil-based removal
Because it forms a water-resistant film, it can be stubborn to remove with just water or gentle cleansers; an oil-based makeup remover is often needed.
Best for
- Anyone wanting long-wearing eye or face makeup
- People with oily skin who struggle with makeup melting
- Those who live in humid climates
Use caution if
- People who prefer minimal or 'clean' ingredient lists
- Those with very sensitive eyes who react to film-formers
Usage tips
Safety summary
Considered safe for use in cosmetics at typical concentrations. It is not absorbed through the skin and has a low irritation and comedogenic risk. Some individuals may experience mild sensitivity if the film is too occlusive.
Research notes
Limited independent research on this specific copolymer, but it is structurally similar to other polyester film-formers that have a long history of safe use in cosmetics. The Cosmetic Ingredient Review (CIR) panel has reviewed related polyesters and found them safe as used.
Common label clues
- Typical concentration
- 1-10%
- Regulatory status
- Approved for use in cosmetics in the EU, US, and other major markets. No known restrictions at typical use levels.
- Common uses
- Mascara, Eyeliners, Long-wear foundations, Lip products
- Environmental note
- As a synthetic polymer, it is not biodegradable. However, it is used in small amounts and is not considered a major environmental concern compared to microplastics.
Good to know
- This ingredient is not absorbed into the skin; it sits on the surface as a film.
- It is commonly used in 'tubing' mascaras that form tiny tubes around each lash for easy removal with warm water.
Common questions
What is PET Copolymer in beauty products?
This is a man-made plastic-like ingredient that forms a thin, flexible, invisible film on your skin or lashes. It's most often found in long-wear makeup like mascara, eyeliner, and foundation to help them stay put through sweat, humidity, and tears. Think of it as a clear, breathable raincoat for your makeup.
What does PET Copolymer do in a beauty product?
When applied, the liquid polymer dries and links together into a continuous, flexible film. This film physically locks pigment and other ingredients in place, preventing them from smudging, flaking, or transferring. It also helps control the thickness and spreadability of the product.
Is PET Copolymer safe for most people?
Considered safe for use in cosmetics at typical concentrations. It is not absorbed through the skin and has a low irritation and comedogenic risk. Some individuals may experience mild sensitivity if the film is too occlusive.
Who should be careful with PET Copolymer?
People who prefer minimal or 'clean' ingredient lists Those with very sensitive eyes who react to film-formers
Research sources
Ingredient reviews are educational and are not medical advice. Patch test new products and ask a licensed clinician about persistent irritation, allergies, pregnancy-specific questions, or diagnosed skin conditions.